1. Field of Invention
The present invention relates to a method and apparatus for laying a communication wire such as an optical fiber (and including a communication unit which is a colligation of communication wires) into a tubular member or collecting a communication wire from the tubular member in which it has previously been inserted.
2. Description of Related Art
In the optical fiber art, there exists methods for using compressed fluids to lay in optical fiber, or the colligation of optical fibers, in a previously-placed tubular member (or tube). One such method is disclosed in Japanese Patent Unexamined Publication No. 59-104607.
FIG. 8 (Prior Art) illustrates the method and apparatus for laying a wire according to the prior art. According to this prior art, a communication wire 1 is supplied from a supply reel 2. Both the wire 1 and the supply reel 2 are under atmospheric pressure. The communication wire is to be inserted into a tubular member 5, which tubular member 5 has previously been disposed within a cable 4, by means of a pressure transfer head 3 (the tubular member 5 will be referred to as a previously-placed tubular member.) The pressure transfer head 3 is coupled with a compressor 6. The compressor 6 supplies the pressure transfer head 3 with a compressed fluid at a pressure somewhere above the atmospheric pressure. With this compressed fluid, the wire 1 is pressed and transferred into the previously-placed tubular member 5.
In order to accomplish the task of laying or collecting a communication wire utilizing the known apparatus and method, however, the following problems are encountered:
First, because the communication wire 1 enters the pressure head 3 at an entrance point which is under atmospheric pressure, the pressure fluid tends to leak from the pressure head 3 at that entrance, and further, because the fluid within the pressure head is under pressure, the entrance of the wire 1 into the pressure head 3 is resisted. Because this resistance impedes the transfer of the wire 1, and because the fluid leakage must be compensated for, the known methods and apparatus must be provided with a compressor having a large fluid delivery.
Second, in actual use of the known apparatus, the reel supply 2, the pressure transfer head 3, and the compressor 6 must all be transported directly to the wire laying site. The wiring laying site is frequently not easily reached, nor is it generally a convenient place to transport the above-mentioned equipment to. For example, the wire laying site may well be located inside a building or in a tunnel under a manhole. Accordingly, it is difficult to lay communication wire at such a site while still using the known apparatus and methods.
Third, utilizing the known methods in apparatus, adjustment of the wire transport speed is also difficult. In transferring the wire 1, the transfer speed must be adjusted wherever the previously-placed tubular member 5 bends or lifts (changes elevation). As previously mentioned, because the pressure head 3 generates a force which tends to resist the entrance of the wire 1, it is difficult to adjust the wire transfer speed utilizing the known methods and apparatus.
Finally, utilizing the known methods and apparatus, it is difficult to take-up the communication wire once it has been inserted into the previously-disposed tubular member such that it can readily be used again. This is because in using the known methods and apparatus, the communication wire is collected by being reversely fed at an irregular speed while being subject to constant vibration. This combination of irregular speed and constant vibration causes the quality of the communication wire thus removed to be seriously degraded.